Excessive Heat — Woodbury, Iowa

2025-06-20 to 2025-06-22 · Woodbury, Iowa

Event narrative

Daily afternoon and evening heat indices ranged from 105 to 115 degrees with a maximum heat index of 115 degrees at a personal weather station near Washta on June 20, 112 degrees at a road weather site near Sioux City, 109 degrees at a personal weather station in Sioux City, and 106 degrees near Sergeant Bluff.

Wider weather episode

The upper-level pattern experienced amplification of an eastern U.S. ridge and western U.S. trough, which locked a low-level frontal boundary in place from western Nebraska through central South Dakota into the Great Lakes. This allowed for heat to spread northward as very high dew point readings pooled across the area with the recent wet conditions. This multi-day dangerous heat event featured daytime heat index readings from 100 to 120 degrees, with nighttime low temperatures remaining from the mid 70s to lower 80s.

Source: NOAA Storm Events Database, event_id 1277676. Narrative written by the NWS forecast office that issued the report.